Let piecrust stand at room temperature for about 15 minutes; peel off plastic sheets. Place crust in a 9-inch glass pie plate; press firmly against sides and bottom. Fold back excess crust; crimp and flute. Prick bottom and sides with fork.
Bake untl lightly browned, about 8 minutes. Transfer pie plate to a wire rack; cool completely.
In a microwave safe bowl, combine caramels and water. Microwave on HIGH at 1 minute intervals, stirring well after each interval, until mixture is smooth, 2-3 minutes. Let cook for 10 minutes.
In a large bowl, beat eggs with a fork.
Add brown sugar, sour cream, pecans, vanilla, and caramel mixture; mix well.
Pour mixture into crust. Reduce oven heat to 350°F Bake until filling is set, about 30 minutes.
Transfer pie plate to wire rack; cool completely. Refrigerate until thoroughly chilled.
In a microwave-safe bowl, combine cream and milk chocolate chips. Microwave on HIGH for 1 minute; whisk until chips are melted and mixture is smooth. Cool to room temperature, about 1 hour.
Using an electric mixer set on high speed, beat chocolate mixture just until it lightens in color; spoon over pie and spread to edges of crust. Refrigerate untl firm, about 2 hours.
Put which and semisweet chocolates in two small bowls over pans of simmering water; stir each until melted. Dip half of the pecans in white chocolate and half in semisweet. Cool on baking sheet until set; place decoratively on pie.